This is Your Brain on Sugar

Is it solid science or scare-'em-straight hyperbole??

​New studies suggest that we can get hooked on sugar just like drugs or alcohol.

In the summer of 2014, registered dietitian Carole Bartolotto asked 20 of her colleagues at California-based managed-care giant Kaiser Permanente to do the unthinkable: cut out all added sugars and artificial sweeteners for two weeks. To rally her coworkers, she used the motivation tactic du jour and called it a "challenge." The instructions: No added sweeteners of any kind (including honey, stevia, Splenda). No processed foods exceeding five grams of added sugar per serving. And no more than five servings of fresh fruit daily—no fruit juice.

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The results surprised Bartolotto. After two weeks, 95 percent of participants reported that sugary foods and drinks tasted sweeter or too sweet. And 75 percent said that foods such as baby carrots, even crackers, tasted sweet. "It only took two weeks for people to completely reset their palates," she says.

The first part of the experiment wasn't pretty, however. More than half the group described intense, uncomfortable sugar cravings that only subsided after three days. For another third, it took six days. Participants suffered headaches, reported that the diet modification required a "great deal of willpower," and called the first days "brutal."

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Many of us have observed that sugar begets sugar. Think of the holidays, when after days of bingeing on cookies, pie, and the neighbor's homemade peppermint bark, you wake up the next morning with a great idea: gingerbread Bundt cake for breakfast!

But Bartolotto's small survey, published in the peer-reviewed Permanente Journal, is fascinating because it's one of the few to document that we go through an actual withdrawal process when we stop eating sugar. It also confirms the informal stories shared over the years by sugar detoxers: that eliminating sugar causes low energy, depression, flulike symptoms, and mental fogginess, at least temporarily.

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The evidence documenting the danger of the sweet stuff has been mounting for some time. Added sugar has long been linked to the rise in obesity and type 2 diabetes—and now we can add early death. According to a 15-year studypublished in the Journal of the American Medical Association: Internal Medicine, U.S. adults of all ages whose daily calorie count consisted of 17 to 21 percent added sugar (not naturally found in food) were more than a third more likely to die of heart disease than those who kept their consumption to less than 8 percent of the total—regardless of their BMIs. The mechanism is unclear, but the authors theorize it might be linked to inflammation, along with increased blood pressure and triglyceride fat levels. Other studies have linked added sugar to cancer risk, depression, and dementia.

Last year, the World Health Organization advised that adults eat no more than six teaspoons, or 100 calories, of sugar a day (about the amount in one pumpkin pie Clif Bar). For comparison, the Centers for Disease Control estimates that U.S. women between the ages of 20 and 39 consume an average of 275 calories of sugar daily; for those between 40 and 59, it's 235.

Yet the public narrative has taken a new twist. Sugar is no longer simply unhealthy; it's increasingly being called "addictive"—and not just in a dramatic, "OMG! I can't stop eating Swedish Fish!" kind of way. Though the idea remains controversial, some scientists believe sugar invites compulsive consumption the way drugs and alcohol do.

Brain imaging studies over the years have shown that drugs such as heroin and cocaine tamper with the brain's neural circuitry by inducing the release of dopamine, which regulates pleasure and decision-making—and the same brightly colored blobs light up in a brain "on sugar." But as provocative as that sounds, such similarities are only the beginning of the scientific story; the same brain areas are also activated by sex and taking a spin class. To try to tease out sugar's addictive properties, a study published in 2012 in the American Journal of Clinical Nutrition examined functional MRI scans of 151 normal-weight adolescents who consumed a chocolate milk shake; those who reported eating ice cream frequently in normal life showed less-responsive reward regions, the authors wrote, "paralleling the tolerance observed in drug addiction."

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In a study from Princeton University in 2007, rats had access to a sugar solution for 12 hours every day for a month, and the fluctuations in dopamine mirrored those found in opiate addicts, psychologist Nicole Avena, PhD, and her coauthors concluded. Dopamine rose each time the rats binged on sugar and dropped during the deprivation period. (During normal eating, the dopamine response evens out as each subsequent bite delivers less pleasure.) Avena's rats also behaved like drug addicts, exhibiting a loss of control over consumption and, during withdrawal, suffering from anxiety, depression, and even tremors.

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The notion that some people can become "addicted" to food has been around since 1960, when Overeaters Anonymous was founded, based on the 12-step approach to treat alcoholism. But popular interest in the concept escalated in 2009 when Ashley Gearhardt, PhD, now an assistant professor of clinical science at the University of Michigan, helped develop what's called the Yale Food Addiction Scale. The scale is a battery of questions intended to detect signs of dependence, like "Over time, I have found that I need to eat more and more to get the feeling I want, such as reduced negative emotions or increased pleasure." Patients who struggle with at least three of the eight features of addiction qualify for the relatively new diagnosis "binge eating disorder," added to the Diagnostic and Statistical Manual of Mental Disorders in 2013.

Critics of the Yale Scale, however, say it relies on notoriously inaccurate self-reporting and subjective understanding of concepts such as withdrawal and agitation. They worry people will use the food-addiction diagnosis to justify regular benders. Also, its high correlation with other disorders, such as bulimia nervosa, is suspect. "Whatever the Yale Scale is measuring has a lot to do with other pathologies," says University of Cambridge psychiatry researcher Hisham Ziauddeen, PhD. "Is the scale measuring a distinctive entity, or is it picking up on other problems?"

Going more granular, so to speak, sugar shouldn't be likened to opiates or alcohol because sudden withdrawal from the latter two can be life threatening, says Peter Pressman, MD, vice president of public health, medicine, and nutrition for the Daedalus Foundation, a nonprofit research institute. "It's way too glib to put food cravings in the same category as real substance addiction," he says. "The person coming off opiates is tearing their skin off or climbing the wall."

Skeptics also chafe at the supposition that we can become addicted to something we need to live. We're wired to desire sweet substances, says Caroline Davis, PhD, a psychologist at York University in Toronto. Sugar is converted quickly into glucose and was adaptive for survival; during our hunting and gathering days, sweetness was a sign that food was safe. "Things that were toxic tasted bitter," she says. "Nowadays we don't worry about that. We have the FDA."

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But perhaps the largest issue for sugar-addiction doubters is, Where's the evidence for it among creatures other than lab rodents? While compelling brain imagery shows overactive reward circuits in obese people or those resistant to the satiety hormone leptin, the results are inconsistent in the general population, says Kent Berridge, PhD, professor of psychology and neuroscience at the University of Michigan. "The big question is whether it's a few people who are showing these brain overreactions," he says, "or whether nearly all of us have the capacity to be addicted to our most tempting favorite foods."

Yet in a study published last year in PLOS One, researchers found that it was the kind of food that gave people problems, rather than the kind of people who ate it. One hundred twenty randomly selected University of Michigan undergraduates, with an average BMI of 23, reviewed a list of 35 foods and indicated which were the hardest to cut back on or inspired out-of-control eating. The top five selected—chocolate, ice cream, French fries, pizza, and cookies—contain a lot of added sugar, as well as fat and refined carbs, which spike blood sugar.

The study authors concluded that the worst trigger foods were those that had been altered to change how they're absorbed, just as coca leaves and grapes must be processed to become potent cocaine and wine. "People aren't getting addicted to the sugar in an apple," Gearhardt says.

In a disturbing example of what goes wrong when food is created in a lab, two neuroscientists from the Scripps Research Institute, a nonprofit biomedical research organization, published a study in 2010 in Nature Neuroscience in which they tested what happened when rats binged on what seems like a stoner's fantasy menu: grocery-store cheesecake, pound cake, canned frosting, chocolate, sausage, and bacon. Not surprisingly, perhaps, the rats that had extended access to the junk food ate almost twice as many calories as control rats and quickly gained weight.

But here's where it gets interesting: The control rats and the newly fat rats were then both allowed to eat the cheesecake (which had been the junk-food favorite), but when they went back for seconds, their feet were shocked. The rats that had had little or no prior access to the junk food backed away from the cake, but those who'd already been exposed kept right on eating through the pain. Finally, when the animals were put back on their regular diet, they went on a two-week-long hunger strike, voluntarily starving themselves, in essence, rather than returning to "healthy" food.

Although the rats enjoyed the processed meats, they didn't go as crazy eating them, suggesting that Swedish Fish fans perhaps shouldn't be lumped with bacon-wrapped chorizo lovers. While fat can also spur dopamine release, it affects the brain's satiety signals differently, says Avena, now an assistant professor of pharmacology at the Mount Sinai school of medicine in New York City and the author of Why Diets Fail (Because You're Addicted to Sugar) "You can't really binge on greasy hamburgers because you get full from them quickly, but we don't see that happening with sugary, high-carb foods," she says. "It could take a half hour to feel full, and by then you've eaten a half-box of Oreos."

In fact, in a study published last summer in Eating Behaviors, Michelle Joyner, a doctoral student in clinical psychology at the University of Michigan, examined the differences among 283 people, some of whom primarily craved sweets and refined carbs, while others generally preferred fat. The sugar fiends were more likely to binge, but the fat fans had higher BMIs. "Sugar and fat may both be problematic, but through different mechanisms," Joyner says. "But foods high in fat and sugar, like chocolate cake, might be particularly risky because fat makes food taste better, so it's likelier to be overeaten. Plus, the high sugar content could make one likelier to consume it in an addictive way."

Still, despite what you learned in high school health class, only about 15 percent of people who try drugs or alcohol develop dependencies, Ziauddeen says. The next direction for research is delineating why some of us are more sugar-sensitive than others. In the meantime, if you're someone who just has to finish the pint of ice cream, perhaps the addiction analogy might help you cut back—just like the knowledge of a family history of alcoholism might move you to cork the wine before finishing the whole bottle.

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